Pestpatrol goes in-depth into the wet truth surrounding silverfish infestations in houses across London.

You turn on the bathroom light at night to spot something small and silver scurrying across the bathroom tile. Gone before you can catch it.

You’re probably not imagining it—it’s likely a silverfish—and if you’re starting to see them regularly, your home is telling you something important: there is too much dampness.

At Pestpatrol, we have been involved in hundreds of silverfish cases across London from historic townhouses in Camden to converted flats in Hackney.

What many of them appear to have in common is something that nobody is prepared to admit—excess moisture, poor ventilation, or both.

In this article, we peel back the wallpaper (sometimes literally) that explains why silverfish are attracted to damp homes, how to spot the signs early, and what you can do if these prehistoric pests have moved in.

What Are Silverfish?

Before we get into the moisture bit, let’s talk about the pest itself.

Silverfish are wingless insects that gained their name for their metallic colour and fish-like wriggling motion when they scurry.

Silverfish are approximately 12mm long, have a hasty, shy nature, and are primarily active at night.

You are unlikely to readily see them unless you disturb them or, of course, until there are large numbers of them.

Silverfish are ancient creatures and have changed little in the last 400 million years.

Their ability to survive makes dealing with them difficult, especially when a home has requirements that roll out a red carpet.

Why Dampness Attracts Silverfish

Silverfish do not simply tolerate dampness… they thrive in it.

Think of a humid bathroom with paint peeling off the walls or a basement with a musty smell; these are the sort of places silverfish like to make their homes.

So why do silverfish thrive in these areas?

The answer might be distilled into 3 main ideas:

1. Moisture is Lifeblood

Silverfish require a high level of humidity to live (ideally above 75%).
Once removed from the wet environment, they will dehydrate and die off.

This is why you hardly see them in dry or well-ventilated places; there is less moisture for the insects to thrive, live longer in, reproduce faster in, and spread quicker in.

2. Soft Substrates are Delicious

Silverfish are not fussy when it comes to food!

Silverfish primarily feed off starchy materials like;
paper (some how they know the good books from the bad ones),
cardboard, glue, fabric, even the binding of an old book.

In wet homes, these materials soften and become even easier to eat.

Those rolls of peeling wallpaper?
Charles’ mildewy boxes in the loft?
Silverfish will find an entire smorgasbord in no time.

3. Damp Spaces = Hiding Spots

Moisture usually means some sort of decay;
rotting skirting boards, bubbling or peeling paint, or gaps in tiles.

These areas all provide perfect hiding, breeding and laying areas for silverfish to lay undetected.

Common Damp Locations where Silverfish Take Up Residence

Although silverfish are predominantly found in bathrooms, and use them as home ‘base’, they are happy to set up house anywhere where dampness is present.

London’s building stock means it is especially vulnerable to silverfish infestation.

Common areas we regularly find silverfish are:

• Bathrooms with leaking pipes or poor extractor fans
• Kitchens, especially under sinks and behind appliances
• Cellars and basements, especially with unsealed floors or walls
• Lofts, where a build up of condensation goes unnoticed
• Cupboards backing onto external walls
• Wall cavities; especially in properties with rising damp or poor insulation

Signs that you may have a silverfish issue

Silverfish can be elusive but they are not invisible.

What to look out for:

• Sightings in the dark – in particular, in wet rooms.
• Yellow stains or droppings on paper, cardboard or fabric.
• Feeding marks, which look like irregular holes or notches.
• Shed skins left behind as they grow.
• Trapped insects – you may find them in the bath or below sinks.

And remember – seeing one does not necessarily mean it is the only one.

Silverfish breed rapidly and tend to live in groups.

If you are seeing them on a regular basis, that’s a signal that needs addressing.

Why Damp is Generally Ingrained in London Homes

Let’s be honest, London’s weather is not helping.

However, many homes in London have inherent structural or design characteristics that will make damp a chronic issue.

• Older buildings which probably have no ventilation and cracked render.
• Converted flats which have either no insulation or damp-proofing and…
• Basements that were never designed to be living spaces.
• Blocked gutters or leaking roofs that let water in.
• And condensation from the heating within a more sealed modern home while cooking etc.

No wonder Silverfish are so consistent throughout the Capital.

Getting Rid of Silverfish: What Works and What Doesn’t

Silverfish control is about controlling the pest and the environment which supports it.

Here are our recommendations with Pestpatrol.

Deal with the Moisture First.

You can kill the bugs, but if you leave the moisture behind… They’re coming back! Stop here:

• Fix leaks – check under sinks, around toilets, and behind appliances
• Improve ventilation – use extractor fans in bathrooms and kitchens
• Buy a dehumidifier, especially in basements or poorly ventilated areas
• Clear clutter that might retain moisture or provide hiding spots
• Insulate well, especially in lofts and around cold exterior walls

Professional Silverfish Control

It is true that DIY sprays may kill a few stragglers, but when it comes to infestations, you usually need a targeted treatment.

At Pestpatrol, we use a combination of :

• Residual insecticides in key harbourage areas
• Insecticidal dusts applied in cracks and voids
• Monitoring traps for assessing the extent of the infestation
• Long-term prevention advice specific to the property

We have helped hundreds of homes across London with getting silverfish under control, and we understand that every home is different.

Prevention Tips: Keeping Silverfish Out for Good

Now that you have evicted them, the trick is making sure they don’t come back.

Here’s some of what we tell our clients:

• Keep humidity below 50 per cent
• Seal all cracks and crevices in walls, skirting and floors
• Declutter – particularly lofts, cupboards and storage areas
• Use airtight containers for papers, clothing and cardboard
• Maintain extractor fans, particularly for steam after a shower or cooking
• Check periodically, particularly during months of colder and wetter weather

Silverfish are annoying and persistent. If they are dealt with right; they don’t stand a chance.

When to Call in the Professionals

You don’t have to live with silverfish.

If you are seeing them on a regular basis or suspect that they are ruining your belongings, it’s time to call in the professionals.

At Pestpatrol, we’ve seen infestations living behind a skirting board, inside a boiler cupboard, and even in boxed-up books stored under beds.

When in doubt, let us have a look.

It might often be what you can’t see that is the issue.

Final Thoughts: A Damp Home Is An Invitation

Silverfish are tough.
They’ve existed longer than the dinosaurs and they’re not going to leave easily. But they can be managed — as long you tackle the factors enabling them to thrive.

Dampness is not just inconvenient. It’s a red flag to pests including silverfish.

So next time you see a silver flicker vanish behind the bath panel, don’t dismiss it.
It may be trying to tell you something that is important.

Need help with silverfish in London?

Visit our Silverfish Control Page to learn more about how Pestpatrol can help you get to the root cause and reclaim your home.

Because when it comes to pests, we don’t only treat the symptoms, we fix the cause.